This Guide provides a step-by-step instruction manual for jurisdictions across the U.S. and globally who wish to create science-based pathways to net zero. The Guide distills the high-level process undertaken by the County of San Diego in the creation of the 2022 San Diego Regional Decarbonization Framework Technical Report, highlights the enabling factors for success, and serves as a toolkit for other communities to follow in their own pursuit of long-term decarbonization planning. The Guide aims to share the process undertaken by San Diego County to help equip researchers, scientists, and political leaders across the U.S. and beyond with the resources they need to localize and advance pathways to regional decarbonization during this decisive Decade of Action.